Affective forecasting is the forecasting of one’s emotional state. Such prediction is affected by various kinds of cognitive biases. Daniel Gilbert (social psychology at Harvard University) and researcherlike Timothy Wilson (University of Virginia) and George Loewenstein (Carnegie Mellon University), have studied these cognitive biases, calling them “empathy gap” and “impact bias”.

Examples of the impact bias include over-estimating emotional reactions to elections, movie clips, Valentine’s Day, football games, etc. Reasons for the impact bias include focalism (people focus too much on the target event, ignoring peripheral activities that may later occupy their attention and impact their emotional state) and immune neglect (people tend to neglect the role their coping resources will later play in ameliorating distressing affects). As such, those with effective coping strategies are actually more prone to biased affective forecasts.

Example of citations about Affective forecasting:
How we forecast our feelings, and whether those predictions match our future emotional states, had never been the stuff of laboratory research. But in scores of experiments, Gilbert, Wilson, Kahneman and Loewenstein have made a slew of observations and conclusions that undermine a number of fundamental assumptions: namely, that we humans understand what we want and are adept at improving our well-being — that we are good at maximizing our utility, in the jargon of traditional economics. Further, their work on prediction raises some unsettling and somewhat more personal questions. To understand affective forecasting, as Gilbert has termed these studies, is to wonder if everything you have ever thought about life choices, and about happiness, has been at the least somewhat naive and, at worst, greatly mistaken.
—Jon Gertner, “The Futile Pursuit of Happiness,” The New York Times, September 7, 2003

People are generally unaware of the operation of the system of cognitive mechanisms that ameliorate their experience of negative affect (the psychological immune system), and thus they tend to overestimate the duration of their affective reactions to negative events. This tendency was demonstrated in 6 studies in which participants overestimated the duration of their affective reactions to the dissolution of a romantic relationship, the failure to achieve tenure, an electoral defeat, negative personality feedback, an account of a child’s death, and being rejected by a prospective employer.
—Daniel T Gilbert et al., “Immune neglect: A source of durability bias in affective forecasting,” Journal of Personality & Social Psychology, September 1, 1998

SUSAN FISKE: Can we become more accurate in affective forecasting?

DANIEL GILBERT: Probably, but first we should ask whether or not we want to. It’s very easy to see somebody making a logical error and say, “Well, you ought not to have made it.” But logical errors can serve an important purpose in human cognition. Imagine a world in which some people realize that external events have much less impact than others believe they do. Those who make that realization might not be particularly motivated to change the external events. But one of the reasons we protect our children, for example, is that we believe we would be devastated if they were harmed or killed. So these predictions may be very effective in motivating us to do the things we as a society need to do, even though they might be inaccurate on an individual level. Anyone who wanted to cure affective forecasters of their inferential ills would be wise to measure both the costs and benefits of forecasting errors.
—”Forecasting the future: why our inability to predict emotion may be beneficial,” Psychology Today, November, 2002

“The research reviewed in this chapter underscores the importance of everyday emotional time travel. People’s predictions about how they will feel in the future shape many of their decisions, though under certain conditions people place surprisingly little weight on their affective forecasts in decision-making. Supporting the validity of decisions that are based on affective forecasts, most studies suggest that forecasts do reliably predict experiences, though we know relatively little about when, why, and for whom the relationship between forecasts and experiences is stronger or weaker. We do know that specific biases in forecasting can be readily eliminated, and there is a smattering of recent evidence that some people may be better forecasters than others. Finally, while common forms of affective forecasting errors may not interfere with the survival of our species, the shortcomings of emotional time travel have important ramifications for individual, interpersonal, and societal well-being.”

People prefer to make changeable decisions rather than unchangeable decisions because they do not realize that they may be more satisfied with the latter. Photography students believed that having the opportunity to change their minds about which prints to keep would not influence their liking of the prints. However, those who had the opportunity to change their minds liked their prints less than those who did not (Study 1). Although the opportunity to change their minds impaired the postdecisional processes that normally promote satisfaction (Study 2a), most participants wanted to have that opportunity (Study 2b). The results demonstrate that errors in affective forecasting can lead people to behave in ways that do not optimize their happiness and well-being.